This past weekend the European Union took a significant step that will have a positive impact on the United States. Despite having rejected the Treaty of Lisbon one year ago, Irish voters approved it – thereby removing the last major roadblock before its full implementation.

The treaty aims to bring EU institutions into the 21st century, streamline its decisionmaking machinery, reinforce accountability, and improve its ability to address domestic and global issues.

It will make the EU a stronger foreign-policy partner of the US when facing common threats, including the Iranian nuclear challenge, climate change, international terrorism, and continued conflict in the Middle East.

All of this should come as a relief to critics in the US who have maintained that the EU has been unfairly shirking its burden of global responsibilities.

Opponents see the Lisbon Treaty as part of a federalist agenda threatening national sovereignty. But the treaty does no such thing.

Currently, EU foreign policy is not as effective as it could be. That's because of competing and overlapping responsibilities between the foreign-policy representative of the Council of Ministers (which represents the interests of the 27 member states of the EU) and the external affairs commissioner of the European Commission, the EU's executive arm. The former has clout as the voice of the member states, but is hampered by a limited budget and staff and has no diplomatic corps. The latter has a significant budget and staff, but does not speak for the member states.

Under the Lisbon Treaty, the two posts are merged. One individual will help bridge the gap by serving as vice president of the European Commission while primarily representing the 27 national leaders and foreign ministers. The individual, likely to be a high profile politician of international stature, will serve as "High Representative for Foreign and Security Policy" – essentially the EU's foreign minister in all but name.

Secretary of State Henry Kissinger famously quipped that it was difficult for the US to deal effectively with Europe without a single phone number to call. Now it will have one.

Some critics have alleged that the Lisbon Treaty is merely a constitution that creates a superstate. However, it is really a pact between sovereign states, which will continue to call their own shots; the US will continue to have the opportunity to influence the member states individually.

On nearly every foreign- and security-policy issue, the high representative will only be able to act with the unanimous consent of the members. Member states will remain free to formulate and conduct foreign policy, retain national diplomatic services, and be represented in international organizations, including at the Security Council of the United Nations.

Despite this retained sovereignty, the treaty will likely increase the EU's unity and ability to serve as a partner of the US in addressing global challenges, over time. The EU has already shown that it is capable of speaking with one voice on trade policy, despite the internal struggle between free-traders and protectionists.

The treaty also improves the coherence and continuity of the EU as an international actor by appointing a full-time president of the European Council, every 2-1/2 years, instead of rotating in leaders from member states every six months.

The combination of a new president and foreign minister for a Europe that – for the first time in its war-torn history – peacefully unites Western and Eastern Europe into one democratic union, will give Europe a powerful voice in world affairs.

The Irish vote puts an end to almost a decade of debilitating obsession in the EU with institutional reform. If the member states now have the political will to implement the treaty as envisaged, it will represent a major step forward in US-EU relations, which we should welcome.